A humid air gas turbine system designed to increase the turbine output by injecting steam to a gas turbine combustor, increasing the flow rate of the combustion gas flowing into a turbine and increasing the specific heat of combustion gas is found in the techniques disclosed in the Japanese Patent Laid-Open No. 2000-054854 (Patent Literature 1) and Vladimir V. Lupandin, et al., DESIGN, DEVELOPMENT AND TESTING OF A GAS TURBINE STEAM INJECTION AND WATER RECOVERY SYSTEM, Proceedings of ASME TURBO EXPO 2001, 2001-GT-0111 (2001) (Non Patent Literature 1).
The percentage of make-up water required to inject steam is several percent through about ten percent of the air intake mass flow rate of a gas turbine. Since this figure is greater than that of the normal thermal power generation system, a problem has been raised in preparing make-up water.
The aforementioned Patent Literature 1 discloses a water recovery system for recovering wherein the exhaust gas exhausted from the heat recovery steam generator for generating steam using exhaust gas from a gas turbine as a heat source is led to a condenser and the exhaust gas is dehumidified, whereby condensate is separated from the exhaust gas and is recovered as recovered water.
The water recovered by the aforementioned water recovery system is subjected to a process of removing mixtures by means of a dust filter and a deaerator, as well as an ion exchange apparatus wherever required. After that, the treated water is fed to the aforementioned heat recovery steam generator, as disclosed in the Literature.
The aforementioned Non Patent Literature 1 also disclosed a water recovery system wherein exhaust gas exhausted from a heat recovery steam generator is cooled and condensed. After the gas dissolved in this recovered water has been separated and removed by a deaerator, the recovered water is fed to a heat recovery steam generator, as disclosed in the Literature.
According to the aforementioned Non Patent Literature 1, concentration of dissolved oxygen in the recovered water meets the requirements for the water fed to a boiler, and the adverse effect of such impurities as nitrogen dioxide, sodium ion, magnesium ion, calcium ion, iron ion and copper ion can be ignored, as described in the Literature.
Further, the Japanese Patent Laid-open No. 2009-162100 (Patent Literature 2) discloses a system wherein the water recovered from the exhaust gas of an advanced humid air gas turbine is supplied to a humidifier of compressed air and is reused. The recovered water partially extracted from this humidifier is purified and is supplied to the water recovery system.
The technique described in this Patent Literature 2 is provided with a water purification system to reduce the concentration of impurities, not to adjust the value of recovered water. Further, Patent Literature 2 also discloses that the carbon dioxide and nitrogen oxides included in the exhaust gas are absorbed in the recovered water of the water recovery system, with the result that recovered water turns acid.